• 关联关系映射

    目录

    一、一对多关联关系

    1.一对多的一方 

     2.多的一方

    二、多对多 

     三、总结

    一、一对多关联关系

    mysql数据库表 t_hibernate_order、t_hibernate_order_item

    表数据 

    首先先用逆向生成工具生成t_hibernate_order、t_hibernate_order_item

    这两张表对应的model于mapper

    generatorConfig.xml

    1. "1.0" encoding="UTF-8" ?>
    2. generatorConfiguration PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
    3.        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd" >
    4. <generatorConfiguration>
    6. <properties resource="jdbc.properties"/>
    7.  
    9. <classPathEntry location="F:\\Courseware\\SoftwareInstallPath\\maven\\apache-maven-3.5.0-bin\\apache-maven-3.5.0-bin\\mvn_repository\\mysql\\mysql-connector-java\\5.1.44\\mysql-connector-java-5.1.44.jar"/>
    10.  
    12. <context id="infoGuardian">
    13.     
    14.     <commentGenerator>
    15.         <property name="suppressAllComments" value="true"/>
    16.         <property name="suppressDate" value="true"/> 
    17.     commentGenerator>
    18.  
    19.     
    20.     <jdbcConnection driverClass="${jdbc.driver}"
    21.                     connectionURL="${jdbc.url}" userId="${jdbc.username}" password="${jdbc.password}"/>
    22.  
    23.     
    24.     <javaTypeResolver>
    25.         
    26.         <property name="forceBigDecimals" value="false"/>
    27.     javaTypeResolver>
    28.  
    29.     
    30.     
    31.     
    32.     <javaModelGenerator targetPackage="com.zking.ssm.model"
    33.                         targetProject="src/main/java">
    34.         
    35.         <property name="enableSubPackages" value="false"/>
    36.         
    37.         <property name="constructorBased" value="true"/>
    38.         
    39.         <property name="trimStrings" value="false"/>
    40.         
    41.         <property name="immutable" value="false"/>
    42.     javaModelGenerator>
    43.  
    44.     
    45.     <sqlMapGenerator targetPackage="com.zking.ssm.mapper"
    46.                      targetProject="src/main/java">
    47.         
    48.         <property name="enableSubPackages" value="false"/>
    49.     sqlMapGenerator>
    50.  
    51.     
    52.     
    53.     
    54.     
    55.     <javaClientGenerator targetPackage="com.zking.ssm.mapper"
    56.                          targetProject="src/main/java" type="XMLMAPPER">
    57.         
    58.         <property name="enableSubPackages" value="false"/>
    59.     javaClientGenerator>
    60.  
    61.     
    62.     
    63.     
    64.     
    65.     
    66.     
    67.     
    68.     
    69.     
    70.     
    71.     
    72.     
    73.     
    74.  
    75.     <table schema="" tableName="t_hibernate_order" domainObjectName="Order"
    76.            enableCountByExample="false" enableDeleteByExample="false"
    77.            enableSelectByExample="false" enableUpdateByExample="false">
    78.         
    79.         
    80.         
    81.         
    82.     table>
    83.  
    84.     <table schema="" tableName="t_hibernate_order_item" domainObjectName="OrderItem"
    85.            enableCountByExample="false" enableDeleteByExample="false"
    86.            enableSelectByExample="false" enableUpdateByExample="false">
    87.     table>
    88.  
    89. context>
    90. generatorConfiguration>

    生成好了之后注意如图所示：

    1.一对多的一方 

    需求1：通过订单号查询本次订单的详细信息及对应的所以订单信息
    select * from t_hibernate_order o,t_hibernate_order_item oi
    where o.order_id = oi.oid and o.order_id = 9

    数据库里查询出的结果如图所示：

     

     

    OrderVo.java

    1. package com.zking.ssm.model.vo;
    2.  
    3. import com.zking.ssm.model.Order;
    4. import com.zking.ssm.model.OrderItem;
    5.  
    6. import java.util.List;
    7.  
    8. /**
    9.  * @author 敢敢
    10.  * @site www.javajwj.com
    11.  * @company xxx公司
    12.  * @create  2022-08-16 21:40
    13.  *
    14.  * vo类不仅仅包含当前表的信息，还能包含相关联表的信息
    15.  *
    16.  * 当前订单会议一个或者多个订单项，多个订单项必须要集合进行接收
    17.  */
    18. public class OrderVo extends Order {
    19.  
    20. //    通过订单号查询本次订单的详细信息及对应的所以订单信息
    21.     private List orderItems;
    22.  
    23.     public List getOrderItems() {
    24.         return orderItems;
    25.     }
    26.  
    27.     public void setOrderItems(List orderItems) {
    28.         this.orderItems = orderItems;
    29.     }
    30. }

     OrderItemVo.java

    1. package com.zking.ssm.model.vo;
    2.  
    3. import com.zking.ssm.model.Order;
    4. import com.zking.ssm.model.OrderItem;
    5.  
    6. /**
    7.  * @author 敢敢
    8.  * @site www.javajwj.com
    9.  * @company xxx公司
    10.  * @create  2022-08-16 21:43
    11.  *
    12.  * 某一个订单项一定属于某个订单的
    13.  */
    14. public class OrderItemVo extends OrderItem {
    15.     private Order order;
    16.  
    17.     public Order getOrder() {
    18.         return order;
    19.     }
    20.  
    21.     public void setOrder(Order order) {
    22.         this.order = order;
    23.     }
    24. }

     OrderMapper.xml

    1. "1.0" encoding="UTF-8" ?>
    2. mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
    3. <mapper namespace="com.zking.ssm.mapper.OrderMapper" >
    4.   <resultMap id="BaseResultMap" type="com.zking.ssm.model.Order" >
    5.     <constructor >
    6.       <idArg column="order_id" jdbcType="INTEGER" javaType="java.lang.Integer" />
    7.       <arg column="order_no" jdbcType="VARCHAR" javaType="java.lang.String" />
    8.     constructor>
    9.   resultMap>
    10.  
    11.   <resultMap id="OrderVoMap" type="com.zking.ssm.model.vo.OrderVo" >
    12.     
    13.     <result column="order_id" property="orderId">result>
    14.     <result column="order_no" property="orderNo">result>
    15.     
    16.     <collection property="orderItems" ofType="com.zking.ssm.model.OrderItem">
    17.       <result column="order_item_id" property="orderItemId">result>
    18.       <result column="product_id" property="productId">result>
    19.       <result column="quantity" property="quantity">result>
    20.       <result column="oid" property="oid">result>
    21.     collection>
    22.   resultMap>
    23.   <sql id="Base_Column_List" >
    24.     order_id, order_no
    25.   sql>
    26.  
    27.   <select id="queryOrderVoByOrderId" resultMap="OrderVoMap" parameterType="java.lang.Integer" >
    28.    select * from t_hibernate_order o,t_hibernate_order_item oi
    29.     where o.order_id = oi.oid and o.order_id = #{orderId}
    30.   select>
    31.  
    32.  
    33.   <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    34.     select 
    35.     <include refid="Base_Column_List" />
    36.     from t_hibernate_order
    37.     where order_id = #{orderId,jdbcType=INTEGER}
    38.   select>
    39.   <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    40.     delete from t_hibernate_order
    41.     where order_id = #{orderId,jdbcType=INTEGER}
    42.   delete>
    43.   <insert id="insert" parameterType="com.zking.ssm.model.Order" >
    44.     insert into t_hibernate_order (order_id, order_no)
    45.     values (#{orderId,jdbcType=INTEGER}, #{orderNo,jdbcType=VARCHAR})
    46.   insert>
    47.   <insert id="insertSelective" parameterType="com.zking.ssm.model.Order" >
    48.     insert into t_hibernate_order
    49.     <trim prefix="(" suffix=")" suffixOverrides="," >
    50.       <if test="orderId != null" >
    51.         order_id,
    52.       if>
    53.       <if test="orderNo != null" >
    54.         order_no,
    55.       if>
    56.     trim>
    57.     <trim prefix="values (" suffix=")" suffixOverrides="," >
    58.       <if test="orderId != null" >
    59.         #{orderId,jdbcType=INTEGER},
    60.       if>
    61.       <if test="orderNo != null" >
    62.         #{orderNo,jdbcType=VARCHAR},
    63.       if>
    64.     trim>
    65.   insert>
    66.   <update id="updateByPrimaryKeySelective" parameterType="com.zking.ssm.model.Order" >
    67.     update t_hibernate_order
    68.     <set >
    69.       <if test="orderNo != null" >
    70.         order_no = #{orderNo,jdbcType=VARCHAR},
    71.       if>
    72.     set>
    73.     where order_id = #{orderId,jdbcType=INTEGER}
    74.   update>
    75.   <update id="updateByPrimaryKey" parameterType="com.zking.ssm.model.Order" >
    76.     update t_hibernate_order
    77.     set order_no = #{orderNo,jdbcType=VARCHAR}
    78.     where order_id = #{orderId,jdbcType=INTEGER}
    79.   update>
    80. mapper>

    OrderMapper.java

    1. package com.zking.ssm.mapper;
    2.  
    3. import com.zking.ssm.model.Order;
    4. import com.zking.ssm.model.vo.OrderVo;
    5. import org.apache.ibatis.annotations.Param;
    6.  
    7. import java.util.List;
    8.  
    9. public interface OrderMapper {
    10.     int deleteByPrimaryKey(Integer orderId);
    11.  
    12.     int insert(Order record);
    13.  
    14.     int insertSelective(Order record);
    15.  
    16.     Order selectByPrimaryKey(Integer orderId);
    17.  
    18.     int updateByPrimaryKeySelective(Order record);
    19.  
    20.     int updateByPrimaryKey(Order record);
    21.  
    22.     OrderVo queryOrderVoByOrderId(@Param("orderId") Integer orderId);
    23.  
    24. }

    OrderBiz.java

    1. package com.zking.ssm.biz;
    2.  
    3. import com.zking.ssm.model.Order;
    4. import com.zking.ssm.model.vo.OrderVo;
    5. import org.apache.ibatis.annotations.Param;
    6.  
    7. /**
    8.  * @author 敢敢
    9.  * @site www.javajwj.com
    10.  * @company xxx公司
    11.  * @create  2022-08-16 22:00
    12.  */
    13. public interface OrderBiz {
    14.  
    15.     OrderVo queryOrderVoByOrderId(Integer orderId);
    16.  
    17. }

    OrderBizImpl.java

    1. package com.zking.ssm.biz;
    2.  
    3. import com.zking.ssm.mapper.OrderMapper;
    4. import com.zking.ssm.model.Order;
    5. import com.zking.ssm.model.vo.OrderVo;
    6. import org.springframework.beans.factory.annotation.Autowired;
    7. import org.springframework.stereotype.Service;
    8.  
    9. /**
    10.  * @author 敢敢
    11.  * @site www.javajwj.com
    12.  * @company xxx公司
    13.  * @create  2022-08-16 22:01
    14.  */
    15. @Service
    16. public class OrderBizImpl implements OrderBiz {
    17.     @Autowired
    18.     private OrderMapper orderMapper;
    19.     @Override
    20.     public OrderVo queryOrderVoByOrderId(Integer orderId) {
    21.         return orderMapper.queryOrderVoByOrderId(orderId);
    22.     }
    23. }

    测试类：OrderBizImplTest.java

    1. package com.zking.ssm.biz;
    2.  
    3. import com.zking.ssm.model.vo.OrderVo;
    4. import org.junit.Test;
    5. import org.junit.runner.RunWith;
    6. import org.springframework.beans.factory.annotation.Autowired;
    7. import org.springframework.test.context.ContextConfiguration;
    8. import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    9.  
    10. import static org.junit.Assert.*;
    11.  
    12. /**
    13.  * @author 敢敢
    14.  * @site www.javajwj.com
    15.  * @company xxx公司
    16.  * @create  2022-08-16 22:02
    17.  */
    18. @RunWith(SpringJUnit4ClassRunner.class)
    19. @ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
    20. public class OrderBizImplTest {
    21.     @Autowired
    22.     private OrderBiz orderBiz;
    23.  
    24.     @Test
    25.     public void queryOrderVoByOrderId() {
    26.         OrderVo orderVo = orderBiz.queryOrderVoByOrderId(9);
    27.         System.out.println(orderVo);
    28.         orderVo.getOrderItems().forEach(System.out::println);
    29.     }
    30. }

    运行结果如图所示：

     

    我们在pom.xml引入了这个 

     

    我们把实体类的Order.java所以的方法给删除，我们在这里面加一个@Data

    1. package com.zking.ssm.model;
    2.  
    3. import lombok.AllArgsConstructor;
    4. import lombok.Data;
    5. import lombok.NoArgsConstructor;
    6.  
    7. //t_hibernate_order
    8. //相当于添加了set/get方法，同时添加了tostring方法
    9. @Data
    10. //一个是有参构造器一个是无参构造器
    11. //@NoArgsConstructor
    12. //@AllArgsConstructor
    13. public class Order {
    14.     private Integer orderId;
    15.  
    16.     private String orderNo;
    17.  
    18. }

    现在在去运行一下如图所示：把之前的地址换成了数据

      

     2.多的一方

    需求2：通过订单项ID查询出订单项详细信息及所属订单
    select * from t_hibernate_order o,t_hibernate_order_item oi
    where o.order_id = oi.oid and oi.order_item_id=43
    数据库查询出的结果如图所示：

     

    OrderItemMapper.xml

    1. "1.0" encoding="UTF-8" ?>
    2. mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
    3. <mapper namespace="com.zking.ssm.mapper.OrderItemMapper" >
    4.   <resultMap id="BaseResultMap" type="com.zking.ssm.model.OrderItem" >
    5.     <constructor >
    6.       <idArg column="order_item_id" jdbcType="INTEGER" javaType="java.lang.Integer" />
    7.       <arg column="product_id" jdbcType="INTEGER" javaType="java.lang.Integer" />
    8.       <arg column="quantity" jdbcType="INTEGER" javaType="java.lang.Integer" />
    9.       <arg column="oid" jdbcType="INTEGER" javaType="java.lang.Integer" />
    10.     constructor>
    11.   resultMap>
    12.  
    13.   <resultMap id="OrderItemVoMap" type="com.zking.ssm.model.vo.OrderItemVo" >
    14.     
    15.     <result column="order_item_id" property="orderItemId">result>
    16.     <result column="product_id" property="productId">result>
    17.     <result column="quantity" property="quantity">result>
    18.     <result column="oid" property="oid">result>
    19.     
    20.     <association property="order" javaType="com.zking.ssm.model.Order">
    21.       <result column="order_id" property="orderId">result>
    22.       <result column="order_no" property="orderNo">result>
    23.     association>
    24.   resultMap>
    25.  
    26.   <sql id="Base_Column_List" >
    27.     order_item_id, product_id, quantity, oid
    28.   sql>
    29.  
    30.   <select id="queryOrderItemVoByOrderItemId" resultMap="OrderItemVoMap" parameterType="java.lang.Integer" >
    31.   select * from t_hibernate_order o,t_hibernate_order_item oi
    32.     where o.order_id = oi.oid and oi.order_item_id=#{orderItemId}
    33.   select>
    34.  
    35.   <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    36.     select 
    37.     <include refid="Base_Column_List" />
    38.     from t_hibernate_order_item
    39.     where order_item_id = #{orderItemId,jdbcType=INTEGER}
    40.   select>
    41.   <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    42.     delete from t_hibernate_order_item
    43.     where order_item_id = #{orderItemId,jdbcType=INTEGER}
    44.   delete>
    45.   <insert id="insert" parameterType="com.zking.ssm.model.OrderItem" >
    46.     insert into t_hibernate_order_item (order_item_id, product_id, quantity, 
    47.       oid)
    48.     values (#{orderItemId,jdbcType=INTEGER}, #{productId,jdbcType=INTEGER}, #{quantity,jdbcType=INTEGER}, 
    49.       #{oid,jdbcType=INTEGER})
    50.   insert>
    51.   <insert id="insertSelective" parameterType="com.zking.ssm.model.OrderItem" >
    52.     insert into t_hibernate_order_item
    53.     <trim prefix="(" suffix=")" suffixOverrides="," >
    54.       <if test="orderItemId != null" >
    55.         order_item_id,
    56.       if>
    57.       <if test="productId != null" >
    58.         product_id,
    59.       if>
    60.       <if test="quantity != null" >
    61.         quantity,
    62.       if>
    63.       <if test="oid != null" >
    64.         oid,
    65.       if>
    66.     trim>
    67.     <trim prefix="values (" suffix=")" suffixOverrides="," >
    68.       <if test="orderItemId != null" >
    69.         #{orderItemId,jdbcType=INTEGER},
    70.       if>
    71.       <if test="productId != null" >
    72.         #{productId,jdbcType=INTEGER},
    73.       if>
    74.       <if test="quantity != null" >
    75.         #{quantity,jdbcType=INTEGER},
    76.       if>
    77.       <if test="oid != null" >
    78.         #{oid,jdbcType=INTEGER},
    79.       if>
    80.     trim>
    81.   insert>
    82.   <update id="updateByPrimaryKeySelective" parameterType="com.zking.ssm.model.OrderItem" >
    83.     update t_hibernate_order_item
    84.     <set >
    85.       <if test="productId != null" >
    86.         product_id = #{productId,jdbcType=INTEGER},
    87.       if>
    88.       <if test="quantity != null" >
    89.         quantity = #{quantity,jdbcType=INTEGER},
    90.       if>
    91.       <if test="oid != null" >
    92.         oid = #{oid,jdbcType=INTEGER},
    93.       if>
    94.     set>
    95.     where order_item_id = #{orderItemId,jdbcType=INTEGER}
    96.   update>
    97.   <update id="updateByPrimaryKey" parameterType="com.zking.ssm.model.OrderItem" >
    98.     update t_hibernate_order_item
    99.     set product_id = #{productId,jdbcType=INTEGER},
    100.       quantity = #{quantity,jdbcType=INTEGER},
    101.       oid = #{oid,jdbcType=INTEGER}
    102.     where order_item_id = #{orderItemId,jdbcType=INTEGER}
    103.   update>
    104. mapper>

     OrderItemMapper.java

    1. package com.zking.ssm.mapper;
    2.  
    3. import com.zking.ssm.model.OrderItem;
    4. import com.zking.ssm.model.vo.OrderItemVo;
    5. import org.apache.ibatis.annotations.Param;
    6.  
    7. public interface OrderItemMapper {
    8.     int deleteByPrimaryKey(Integer orderItemId);
    9.  
    10.     int insert(OrderItem record);
    11.  
    12.     int insertSelective(OrderItem record);
    13.  
    14.     OrderItem selectByPrimaryKey(Integer orderItemId);
    15.  
    16.     int updateByPrimaryKeySelective(OrderItem record);
    17.  
    18.     int updateByPrimaryKey(OrderItem record);
    19.  
    20.     OrderItemVo queryOrderItemVoByOrderItemId(@Param("orderItemId") Integer orderItemId);
    21.  
    22. }

     OrderItemBiz.java

    1. package com.zking.ssm.biz;
    2.  
    3. import com.zking.ssm.model.vo.OrderItemVo;
    4. import org.apache.ibatis.annotations.Param;
    5.  
    6. /**
    7.  * @author 敢敢
    8.  * @site www.javajwj.com
    9.  * @company xxx公司
    10.  * @create  2022-08-16 22:36
    11.  */
    12. public interface OrderItemBiz {
    13.  
    14.     OrderItemVo queryOrderItemVoByOrderItemId(Integer orderItemId);
    15.  
    16. }

    OrderItemBizImpl.java

    1. package com.zking.ssm.biz.impl;
    2.  
    3. import com.zking.ssm.biz.OrderItemBiz;
    4. import com.zking.ssm.mapper.OrderItemMapper;
    5. import com.zking.ssm.model.OrderItem;
    6. import com.zking.ssm.model.vo.OrderItemVo;
    7. import org.springframework.beans.factory.annotation.Autowired;
    8. import org.springframework.stereotype.Service;
    9.  
    10. /**
    11.  * @author 敢敢
    12.  * @site www.javajwj.com
    13.  * @company xxx公司
    14.  * @create  2022-08-16 22:38
    15.  */
    16. @Service
    17. public class OrderItemBizImpl implements OrderItemBiz {
    18.     @Autowired
    19.     private OrderItemMapper orderItemMapper;
    20.     @Override
    21.     public OrderItemVo queryOrderItemVoByOrderItemId(Integer orderItemId) {
    22.         return orderItemMapper.queryOrderItemVoByOrderItemId(orderItemId);
    23.     }
    24. }

    在我们的OrderItem.java里面加一个@ToString就好了，这样就不会是地址了

    1. package com.zking.ssm.model;
    2.  
    3. import lombok.ToString;
    4.  
    5. @ToString
    6. public class OrderItem {
    7.     private Integer orderItemId;
    8.  
    9.     private Integer productId;
    10.  
    11.     private Integer quantity;
    12.  
    13.     private Integer oid;
    14.  
    15.     public OrderItem(Integer orderItemId, Integer productId, Integer quantity, Integer oid) {
    16.         this.orderItemId = orderItemId;
    17.         this.productId = productId;
    18.         this.quantity = quantity;
    19.         this.oid = oid;
    20.     }
    21.  
    22.     public OrderItem() {
    23.         super();
    24.     }
    25.  
    26.     public Integer getOrderItemId() {
    27.         return orderItemId;
    28.     }
    29.  
    30.     public void setOrderItemId(Integer orderItemId) {
    31.         this.orderItemId = orderItemId;
    32.     }
    33.  
    34.     public Integer getProductId() {
    35.         return productId;
    36.     }
    37.  
    38.     public void setProductId(Integer productId) {
    39.         this.productId = productId;
    40.     }
    41.  
    42.     public Integer getQuantity() {
    43.         return quantity;
    44.     }
    45.  
    46.     public void setQuantity(Integer quantity) {
    47.         this.quantity = quantity;
    48.     }
    49.  
    50.     public Integer getOid() {
    51.         return oid;
    52.     }
    53.  
    54.     public void setOid(Integer oid) {
    55.         this.oid = oid;
    56.     }
    57. }

     测试类OrderItemBizTest.java

    1. package com.zking.ssm.biz;
    2.  
    3. import com.zking.ssm.model.vo.OrderItemVo;
    4. import org.junit.Test;
    5. import org.junit.runner.RunWith;
    6. import org.springframework.beans.factory.annotation.Autowired;
    7. import org.springframework.test.context.ContextConfiguration;
    8. import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    9.  
    10. import static org.junit.Assert.*;
    11.  
    12. /**
    13.  * @author 敢敢
    14.  * @site www.javajwj.com
    15.  * @company xxx公司
    16.  * @create  2022-08-16 22:45
    17.  */
    18. @RunWith(SpringJUnit4ClassRunner.class)
    19. @ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
    20. public class OrderItemBizImplTest {
    21.     @Autowired
    22.     private OrderItemBiz orderItemBiz;
    23.  
    24.     @Test
    25.     public void queryOrderItemVoByOrderItemId() {
    26.         OrderItemVo orderItemVo = orderItemBiz.queryOrderItemVoByOrderItemId(43);
    27.         System.out.println(orderItemVo);
    28.         System.out.println(orderItemVo.getOrder());
    29.     }
    30. }

     运行结果如图所示：

    二、多对多 

     多对多就是两个一对多

    首先先用逆向生成工具生成t_hibernate_book、t_hibernate_book_category、t_hibernate_category，这两张表对应的model与mapper

     generatorConfig.xml

    1.  <table schema="" tableName="t_hibernate_book" domainObjectName="Hbook"
    2.            enableCountByExample="false" enableDeleteByExample="false"
    3.            enableSelectByExample="false" enableUpdateByExample="false">
    4.     table>
    5.  
    6.     <table schema="" tableName="t_hibernate_category" domainObjectName="Category"
    7.            enableCountByExample="false" enableDeleteByExample="false"
    8.            enableSelectByExample="false" enableUpdateByExample="false">
    9.     table>
    10.  
    11.     <table schema="" tableName="t_hibernate_book_category" domainObjectName="HbookCategory"
    12.            enableCountByExample="false" enableDeleteByExample="false"
    13.            enableSelectByExample="false" enableUpdateByExample="false">
    14.     table>

    需求1：根据书籍ID，查询书籍信息及所属所有类别信息

    select * from t_hibernate_book b,t_hibernate_book_category bc,t_hibernate_category c
         where b.book_id = bc.bid and bc.cid = c.category_id and b.book_id = 8

     需求2：根据类别ID，查询类别信息及所包含书籍信息

    select * from t_hibernate_book b,t_hibernate_book_category bc,t_hibernate_category c
         where b.book_id = bc.bid and bc.cid = c.category_id and c.category_id=8

     

    HbookVo.java

    1. package com.zking.ssm.model.vo;
    2.  
    3. import com.zking.ssm.model.Category;
    4. import com.zking.ssm.model.Hbook;
    5.  
    6. import java.util.List;
    7.  
    8. /**
    9.  * @author 敢敢
    10.  * @site www.javajwj.com
    11.  * @company xxx公司
    12.  * @create  2022-08-16 23:18
    13.  */
    14. public class HbookVo extends Hbook {
    15.     private List categories;
    16.  
    17.     public List getCategories() {
    18.         return categories;
    19.     }
    20.  
    21.     public void setCategories(List categories) {
    22.         this.categories = categories;
    23.     }
    24. }

     CategoryVo.java

    1. package com.zking.ssm.model.vo;
    2.  
    3. import com.zking.ssm.model.Category;
    4. import com.zking.ssm.model.Hbook;
    5.  
    6. import java.util.List;
    7.  
    8. /**
    9.  * @author 敢敢
    10.  * @site www.javajwj.com
    11.  * @company xxx公司
    12.  * @create  2022-08-16 23:19
    13.  */
    14. public class CategoryVo extends Category {
    15.     private List hbooks;
    16.  
    17.     public List getHbooks() {
    18.         return hbooks;
    19.     }
    20.  
    21.     public void setHbooks(List hbooks) {
    22.         this.hbooks = hbooks;
    23.     }
    24. }

     加到中间表HbookCategoryMapper.xml，要不然你两边表都要加

    1. <resultMap id="HbookVoMap" type="com.zking.ssm.model.vo.HbookVo">
    2.     <result property="bookId" column="book_id">result>
    3.     <result property="bookName" column="book_name">result>
    4.     <collection property="categories" ofType="com.javaxl.ssm.model.Category">
    5.       <result property="categoryId" column="category_id">result>
    6.       <result property="categoryName" column="category_name">result>
    7.     collection>
    8.   resultMap>
    9.  
    10.   <resultMap id="CategoryVoMap" type="com.zking.ssm.model.vo.CategoryVo">
    11.     <result property="categoryId" column="category_id">result>
    12.     <result property="categoryName" column="category_name">result>
    13.     <collection property="hbooks" ofType="com.javaxl.ssm.model.Hbook">
    14.       <result property="bookId" column="book_id">result>
    15.       <result property="bookName" column="book_name">result>
    16.     collection>
    17.   resultMap>
    18.  
    19.   <select id="queryByBookId" resultMap="HbookVoMap" parameterType="java.lang.Integer">
    20. select * from t_hibernate_book b,t_hibernate_book_category bc,t_hibernate_category c
    21.      where b.book_id = bc.bid and bc.cid = c.category_id and b.book_id = #{bookId}
    22.  select>
    23.   <select id="queryByCid" resultMap="CategoryVoMap" parameterType="java.lang.Integer">
    24. select * from t_hibernate_book b,t_hibernate_book_category bc,t_hibernate_category c
    25.      where b.book_id = bc.bid and bc.cid = c.category_id and c.category_id=#{cid}
    26.   select>
    HbookCategoryMapper.java

     

    1. package com.zking.ssm.mapper;
    2.  
    3. import com.zking.ssm.model.HbookCategory;
    4. import com.zking.ssm.model.vo.CategoryVo;
    5. import com.zking.ssm.model.vo.HbookVo;
    6. import org.apache.ibatis.annotations.Param;
    7.  
    8. public interface HbookCategoryMapper {
    9.     int deleteByPrimaryKey(Integer bcid);
    10.  
    11.     int insert(HbookCategory record);
    12.  
    13.     int insertSelective(HbookCategory record);
    14.  
    15.     HbookCategory selectByPrimaryKey(Integer bcid);
    16.  
    17.     int updateByPrimaryKeySelective(HbookCategory record);
    18.  
    19.     int updateByPrimaryKey(HbookCategory record);
    20.  
    21.     HbookVo queryByBookId(@Param("bookId") Integer bookId);
    22.  
    23.     CategoryVo queryByCid(@Param("cid") Integer cid);
    24. }
    HbookCategoryBiz.java
    1. package com.zking.ssm.biz;
    2.  
    3. import com.zking.ssm.model.vo.CategoryVo;
    4. import com.zking.ssm.model.vo.HbookVo;
    5. import org.apache.ibatis.annotations.Param;
    6.  
    7. /**
    8.  * @author 敢敢
    9.  * @site www.javajwj.com
    10.  * @company xxx公司
    11.  * @create  2022-08-16 23:27
    12.  */
    13. public interface HbookCategoryBiz {
    14.  
    15.     HbookVo queryByBookId(Integer bookId);
    16.  
    17.     CategoryVo queryByCid(Integer cid);
    18. }
    HbookCategoryBizImpl.java
    1. package com.zking.ssm.biz.impl;
    2.  
    3. import com.zking.ssm.biz.HbookCategoryBiz;
    4. import com.zking.ssm.mapper.HbookCategoryMapper;
    5. import com.zking.ssm.model.vo.CategoryVo;
    6. import com.zking.ssm.model.vo.HbookVo;
    7. import org.springframework.beans.factory.annotation.Autowired;
    8. import org.springframework.stereotype.Service;
    9.  
    10. /**
    11.  * @author 敢敢
    12.  * @site www.javajwj.com
    13.  * @company xxx公司
    14.  * @create  2022-08-16 23:28
    15.  */
    16. @Service
    17. public class HbookCategoryBizImpl implements HbookCategoryBiz {
    18.     @Autowired
    19.     private HbookCategoryMapper hbookCategoryMapper;
    20.     @Override
    21.     public HbookVo queryByBookId(Integer bookId) {
    22.         return hbookCategoryMapper.queryByBookId(bookId);
    23.     }
    24.  
    25.     @Override
    26.     public CategoryVo queryByCid(Integer cid) {
    27.         return hbookCategoryMapper.queryByCid(cid);
    28.     }
    29. }
    HbookVo.java  加一个ToString不然生成的就是地址
    1. package com.zking.ssm.model.vo;
    2.  
    3. import com.zking.ssm.model.Category;
    4. import com.zking.ssm.model.Hbook;
    5. import lombok.ToString;
    6.  
    7. import java.util.List;
    8.  
    9. /**
    10.  * @author 敢敢
    11.  * @site www.javajwj.com
    12.  * @company xxx公司
    13.  * @create  2022-08-16 23:18
    14.  */
    15. @ToString
    16. public class HbookVo extends Hbook {
    17.     private List categories;
    18.  
    19.     public List getCategories() {
    20.         return categories;
    21.     }
    22.  
    23.     public void setCategories(List categories) {
    24.         this.categories = categories;
    25.     }
    26. }
    Category.java 也生成一个@ToString
    1. package com.zking.ssm.model;
    2.  
    3. import lombok.ToString;
    4.  
    5. @ToString
    6. public class Category {
    7.     private Integer categoryId;
    8.  
    9.     private String categoryName;
    10.  
    11.     public Category(Integer categoryId, String categoryName) {
    12.         this.categoryId = categoryId;
    13.         this.categoryName = categoryName;
    14.     }
    15.  
    16.     public Category() {
    17.         super();
    18.     }
    19.  
    20.     public Integer getCategoryId() {
    21.         return categoryId;
    22.     }
    23.  
    24.     public void setCategoryId(Integer categoryId) {
    25.         this.categoryId = categoryId;
    26.     }
    27.  
    28.     public String getCategoryName() {
    29.         return categoryName;
    30.     }
    31.  
    32.     public void setCategoryName(String categoryName) {
    33.         this.categoryName = categoryName;
    34.     }
    35. }

    生成一个测试类   HbookCategoryBizImplTest.java

    1. package com.zking.ssm.biz.impl;
    2.  
    3. import com.zking.ssm.biz.HbookCategoryBiz;
    4. import com.zking.ssm.model.vo.HbookVo;
    5. import org.junit.Test;
    6. import org.junit.runner.RunWith;
    7. import org.springframework.beans.factory.annotation.Autowired;
    8. import org.springframework.test.context.ContextConfiguration;
    9. import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    10.  
    11. import static org.junit.Assert.*;
    12.  
    13. /**
    14.  * @author 敢敢
    15.  * @site www.javajwj.com
    16.  * @company xxx公司
    17.  * @create  2022-08-16 23:30
    18.  */
    19. @RunWith(SpringJUnit4ClassRunner.class)
    20. @ContextConfiguration(locations={"classpath:applicationContext-mybatis.xml"})
    21. public class HbookCategoryBizImplTest {
    22.     @Autowired
    23.     private HbookCategoryBiz hbookCategoryBiz;
    24.  
    25.     @Test
    26.     public void queryByBookId() {
    27.         HbookVo hbookVo = hbookCategoryBiz.queryByBookId(8);
    28.         System.out.println(hbookVo);
    29. //        书籍所关联的类别
    30.         hbookVo.getCategories().forEach(System.out::println);
    31.     }
    32.  
    33.      @Test
    34.     public void queryByCid() {
    35.         CategoryVo categoryVo = hbookCategoryBiz.queryByCid(8);
    36.         System.out.println(categoryVo);
    37.         categoryVo.getHbooks().forEach(System.out::println);
    38.     }
    39. }

     第一个方法运行结果如图所示：

     第二个方法运行结果如图所示：

     

     三、总结

     一对多

    一方：Collection：属性ofType

    多方：associate：属性JavaType

    多对多：就是两个一对多

    vo类：view Object

    entity/model描述数据库表

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  • 原文地址：https://blog.csdn.net/weixin_67465673/article/details/126374291